What is a power supply? (not computer-wise)

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There has been this box in one of my outlets that has been here since I moved in and just now took it off and it says it’s a Class 2 Power Supply. Not an electrician, but why is it there?

In: Technology
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It’s powering something. Maybe a doorbell, or the phone/TV/Internet box.

You’ll need to follow the wire. Or, just unplug it and see what stops working.

Class II only means it’s double insulated, so it can have a 2-prong plug. That doesn’t tell you much.

It could just be a transformer, which turns household AC into some (probably) lower voltage. Or it could be a transformer plus a rectifier and some smoothing circuitry, for turning AC into DC.

If you look on the box, it might have some text about its input and output. They often say “input 120VAC output 5VDC”, something to that effect.

Its kinda in the name, it supplies power

Generally its used to refer to things that take power from the wall and convert it into a low DC voltage that most of your electronics use like USB power supplies or the power bricks that feed laptops.

A Class 2 power supply feeds low voltage DC to some device downstream. The Class 2 refers to a National Electric Code(NEC) rating which limits the max power, voltage, and current that can be provided by the supply so that its outputs are relatively safe to touch which is a good feature for things like Laptop chargers where an average untrained person is going to have access to the live DC connector.

The power supply provides usable electricity to the rest of the computer parts. The standard wall outlet has too high of a voltage for your more delicate components (like little capacitors, microprocessors, etc) so the power supply serves as a bit of a gatekeeper to make sure that the current from your mains electricity doesn’t fry your components. It’s a lot like the charging bricks that plug into the wall and use a USB cable to charge a cell phone.